14/06/2018

Antarctic Ice Melting Faster Than Ever, Studies Show

The Guardian - 

Rate of melt has accelerated threefold in last five years and could contribute 25cm to sea-level rises without urgent action
Scientists warns time is running out to save the Antarctic and its unique ecosystem, with potentially dire consequences for the world. Photograph: Daniel Beltrá/Greenpeace 
Ice in the Antarctic is melting at a record-breaking rate and the subsequent sea rises could have catastrophic consequences for cities around the world, according to two new studies.
A report led by scientists in the UK and US found the rate of melting from the Antarctic ice sheet has accelerated threefold in the last five years and is now vanishing faster than at any previously recorded time.
A separate study warns that unless urgent action is taken in the next decade the melting ice could contribute more than 25cm to a total global sea level rise of more than a metre by 2070. This could lead eventually to the collapse of the entire west Antarctic ice sheet, and around 3.5m of sea-level rise.
Prof Andrew Shepherd, a lead author of the study on accelerating ice loss, said: “We have long suspected that changes in Earth’s climate will affect the polar ice sheets. Thanks to our satellites our space agencies have launched, we can now track their ice losses and global sea level contribution with confidence.”
He said the rate of melting was “surprising.”
“This has to be a cause for concern for the governments we trust to protect our coastal cities and communities,” Shepherd added.
The study, published in Nature, involved 84 scientists from 44 international organisations and claims to be the most comprehensive account of the Antarctic ice sheet to date. It shows that before 2012, the Antarctic lost ice at a steady rate of 76bn tonnes per year - a 0.2mm per year contribution to sea-level rise. However since then there has been a sharp increase, resulting in the loss of 219bn tonnes of ice per year - a 0.6mm per year sea-level contribution.
The second study, also published in Nature, warns that time is running out to save the Antarctic and its unique ecosystem - with potentially dire consequences for the world.
The scientists assessed the probable state of Antarctica in 2070 under two scenarios. The first in which urgent action on greenhouse gas emissions and environmental protection is taken in the next few years, the second if emissions continue to rise unabated and the Antarctic is exploited for its natural resources.
The scenario which plays out largely depends on choices made over the next decade, on both climate-change and on environmental regulation, they conclude.
Co-author Profe Martin Siegert, from the Grantham Institute, said: “Some of the changes Antarctica will face are already irreversible, such as the loss of some ice shelves, but there is a lot we can prevent or reverse.
“To avoid the worst impacts, we will need strong international cooperation and effective regulation backed by rigorous science. This will rely on governments recognising that Antarctica is intimately coupled to the rest of the Earth system, and damage there will cause problems everywhere.”
As well as being a major cause of sea-level rise, scientists say the oceans around Antarctica are a key “carbon sink” - absorbing huge amounts of greenhouse gases helping to mitigate the impacts of climate change.
Siegert said: “If the political landscape of a future Antarctica is more concerned with rivalry, and how each country can get the most out of the continent and its oceans, then all protections could be overturned.
“However, if we recognise the importance of Antarctica in the global environment, then there is the potential for international co-operation that uses evidence to enact changes that avoid ‘tipping points’ – boundaries that once crossed, would cause runaway change, such as the collapse of the west Antarctic ice sheet.”

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